I. Field of the Invention
This invention relates generally to machinery for processing livestock feed, and more particularly to an improved mixer for blending various ingredients to be fed to dairy herds and other agricultural animals.
II. Discussion of the Prior Art
Dairy operations typically include the milking cowherd with some of the cow population in the non-lactation stage (dry cows) and with growing heifers. Distinctly different diets are required for each of these three stages of the lifecycle, resulting in great differences in the volumes and nutrient composition of the feed to be given to such a herd. In that feed is the major cost associated with dairy production, one way to reduce or control feed costs in dairy farms is to maximize the use of forages in rations. For example, high quality legumes and grasses provide dairy cows and heifers with a good source of protein energy, fiber and minerals. Corn silage is a high energy feed that supplies fiber as well as grain. However, poor growing, harvesting and/or drying conditions often result in a low supply of high quality forages. If all low quality forages are fed to dairy cows, decreases in intake often result, and milk production decreases because of insufficient nutrients. When dairy producers are forced to feed low quality forages, one option is to look for low cost alternative or byproduct feeds to substitute for some of the low quality forages in the ration.
Additives to available forages include protein supplements such as soybean meal, canola meal, sunflower meal, dried distillers grains as well as a variety of other byproducts of the milling and brewing industries. A variety of grains is also frequently included in cattle feed with oats, barley and shelled corn being ones more frequently used. Cane and beet molasses can be used to enhance the energy supply and the palatability of the feed mixture.
By blending together all the forages, grains, commodities and protein and mineral-vitamin supplements, cows are less able to selectively consume individual ingredients. Ideally, each bite of feed a cow consumes will contain the same proportion of forages and concentrates. It has been found that by feeding dairy herds a “total mixed ration” (TMR) not only does milk production improve, but feed costs decrease. Feeds previously hard to feed can now be fed and the cow health and/or reproductive performance improves.
Various types of TMR mixers are commercially available and generally fall into one of the following types:
Horizontal auger;
Vertical auger or screw;
Reel; and
Tumbling action within a drum.
Mixers with horizontal augers typically have one or more horizontal augers for mixing the feed ingredients. With multiple-auger mixers, the mixing action occurs when one or two of the augers counter-rotates, moving the feed in opposition to an adjacent auger. Knife sections are often attached to auger flights to cut or tear long stemmed alfalfa hay into pieces of three to four inches in length. However, many horizontal auger mixers do not handle grass hay or baleage well in that these types of feeds tend to wrap around the augers.
Typical prior art vertical auger mixers consist of a tub having a single, center auger or tapered screw. The center auger may typically be powered by a transmission and planetary gearbox. These mixers can make TMR rations in which all the forage is dry hay. Knife sections attached to the flights of the center auger and movable shear or restrictor plates on the tub wall help reduce the particle size of dry hay or baleage. Vertical auger mixers can generally handle large round bales of grass or alfalfa hay.
Reel mixers often combine a set of augers and a reel similar to a combine reel in a hopper. The rotary mixing system lifts feed past the wedging point on the lower side of the auger. The lifting action of the rotor is intended to minimize wedging of alfalfa hay and other long stem forages under the lower auger, potentially preventing the particle size of the forages being mixed from being reduced.
With tumble or chain and paddle mixers, spirals and pans on the interior of the drum lift and tumble the ration. Loading and unloading occurs at different ports on the mixer. Chain and paddle mixers consist of a tub with a chain and paddles on a conveyor that are used to tumble the ration from one end to the other. Some configurations of both types of mixers use a central auger that circulates the feed, moving it to the front of the mixer, where it is either remixed in the tumbling action or delivered to the unloading port. One advantage of this type of mixer over auger or reel mixers is that there is less wear and lower power requirements.
Examples of horizontal mixers are found in the Walter U.S. Pat. No. 3,173,582, the Neier U.S. Pat. No. 5,143,310 and the Mohrlang U.S. Pat. No. 4,707,140.
Likewise, vertical auger mixers are disclosed are the Rowe et al. U.S. Pat. No. 6,575,615, the Miller U.S. Pat. No. 5,240,321, the Schuler U.S. Pat. Nos. 5,601,362 and 5,647,665 and the Stone U.S. Pat. No. 5,429,436.
A tumbler-style mixer is found in the Rule '492 patent.
Mixers can also be classified as being either movable or stationary. The aforementioned Miller '321 patent exemplifies a stationary installation whereas the Rowe et al. '615, the Schuler '362 and '665 and the Stone '436 are all examples of transportable trailer-mounted mixers.
A problem exists with stationary mixers of the vertical auger type in that they must be especially designed to accommodate a placement relative to infeed and discharge conveyors commonly used with such mixers. Also, surrounding building structures must also be taken into account. This presents a problem for the mixer manufacturer in that the location of the discharge door of the mixer tub must conform to a customer's particular layout.
To insure that feed ingredients are mixed in a desired proportion, it would be advantageous that the mixing tub incorporate a scale whereby the weight of each constituent added to the mixing tub is determinable.
The cost of manufacture of a stationary, vertical auger feed mixer can be reduced where a thinner gauge steel sidewall can be used. However, such thinner gauge sidewall may need a reinforcing flange surrounding the upper open end of the tub. In prior art machines, the reinforcing rim comprises an annular plate welded to the upper rim of the tub sidewall. A drawback of this approach has been the fact that feed tends to collect on the rim reinforcement structure that over time will rot, become moldy and may later enter a batch of feed being processed.
Another drawback of prior art, vertical auger, feed mixers is that the optimum auger speed for mixing is slower than that required for discharging the already mixed feed through the tub's discharge opening and on to a discharge conveyor leading to the animal's feeding site.
The present invention obviates each of the above-described shortcomings of the prior art.